#define   _CRT_SECURE_NO_WARNINGS  1
#include<stdio.h>
int main()
{
	float a = 0;
	float b = 0;
	int i;
	b = 1;
	for (i = 1; i <= 100; i++)
	{
		a = a + b / i;
		b = -b;
	}
		printf("%f",a );

	return 0;
}